As one of double-gate type transistors having a structure in which a channel region is sandwiched by a gate electrode for enhancing current controllability by the gate electrode, there is a FinFET (Fin Field Effect Transistor) which is a transistor having a fin structure. In the FinFET, it is important to reduce a width of a fin.
However, since a gate width is also reduced when the width of the fin is reduced, a sufficient drive current may not be obtained. For solving this problem, a FinFET in which a plurality of fins arranged in parallel are formed and a substantial gate width is increased, has been known. This FinFET, for example, is disclosed in JP2007-103455.